Relay circuit



April 1949. H. H. SCHWARTZ 2,468,308

RELAY CIRCUIT Filed May 24}, 1945 FIG.

FIG 2 /NVENTOR H. H. 5CHWARTZ Patented Apr. 26, 1949 RELAY cmovrr Harry H. Schwartz, Montreal, Quebec, Canada,

assignor to Western Electric Company, Incorporated, New York, N. Y., a corporation ol Ncw York Application May 24, 1945, Selifl No. 595,517 4 Claims. (Cl. 175-320) This invention relates to relay circuits and more particularly to circuits in which relays may be continuously energized.

The invention is particularly concerned with relays which operate on the flux neutralizing principle, that is a relay which is normally energized through one Winding to hold a pivoted armature in one position and is operatively energized by two windings, the flux in one of which serves to neutralize the flux in the normaily energized winding and in the other of which serves to move the armature into its alternate position.

In accordance with the present invention, means is provided to permit continuous energizatien of such a relay to held the armature in either position.

More particularly the invention provides a resistance in series with both energizing circuits of such value as to prevent the relay from overheating.

The invention will be more clearly understood from a consideration of the following detailed description in connection with the drawing in which:

Fig. 1 shows a known relay adapted for intermittent operation; and

Fig. 2 shows a similar relay adapted according to the preserxt invention for continuons operation.

The relay cf Fig. 1 has a core l having three pole-piece legs, 2, 3 and 4. Windings 5 and C are wound on leg 2 and winding 1 is wound on leg 4. Winding 5 is energized from source E when switch 8 is closed while windings 6 and 1 are energized in series from source E when key 9 is operated. 'Ihe armature Il! is pivoted at the point H and controls two contacts I! and [3. Switch 5 is normally ciosed to held armature il! against leg 2 and close contact I3. The flux generated in winding 6, when key 3 is operated, opposes that in winding 5, neutralizing the attraction o! leg 2 on the armature in and permitting winding 1 to attract armature l0 against les 4. to close contact l2.

This arrangement has the advantage that there is a magnetic holding force in both positions and therefore the armature is held securely in either position, since the mangeticiorce is greatest when the displacement is least. Such a relay operates very well in locations subject to vibration.

To adapt such a relay to function with either a single winding or all three windings enerzized a number of factors must be considered.

The necessary mathematical calculatlons are based on four fundamental relationships expressed in equations, all of which appear in or are odfly derived from equations appearinz in Sec- 2 tion 5 et the Standard Handbook for Electrical Engineers, Seventh edition. published by McGraw Hill Bock Company, Incorporated 1941.

These equations are:

in which V=the volume available for winding l=length ci a mean turn of the winding n=number cf turns on the winding a=cross-sectionai area of the wire S=space factor of the coil winding in which E, 71 and a are deflned above and R,=totai resistance of the winding r=speciflc reslstivity of the coi! conductor H=knl in which 11. is deflned above and H=ampere turns per inch I=coil current in amperes k=a constant or factor oi Droportionaiitv in which Ris deflned above and P=coil dissipation in Watts E=applied voltage in volts.

Equations 1 and 2 may be combined to eiiminate the factor a, resulting in Equation 3 from Ohm's law may also be Written and combinins (9) with (4) As pointed out in the Handbook, above reterred to, total flux densit across the ple face of a magnet is directly pmportionai to the ampere turns, while the force exerted is proportional to the square of the flux: density. Therefore, the force, represented 1) F, may be ex pressed by where le: is another proportion&lity factor, or. substituting (10) in (11) k cj P-V-S For convenience kik may be renresented by a single proportionality factor in.

From Equation 12 is may be readily seen that for a given winding space, the force is directly proportional to the power dissipated in the (:011. Hence to keep the temperature rise down when the reiay is operated continuously, some modification of the circuits over those shown in Fig. 1 is required. These modifications consist in redesigning the colis and inserting a series resistance as shown at R1 in Fig. 2.

Referring more particulariy to Fig. 2, current is supplied to the relay from a. source having a Voltage E2. "Ihe windings and S on core 2 may be assumed to have resistances R2 and Ra. while the winding on core 4 has a resistance R4. With switch 8 closed to energize winding 5 and hold the armature in the position shown, the power in that coi1 may be expressed as P5C. With switch M closed to also energize windings 5 and 1 the current drain through windings S and 1 increases the current and theteby the voltage drop through resistance R1, in turn W- ering the voltage drop across coil 5 and hence aise lowering the power dissipated in it to a value which may be expressed as F511. 1: the total power dissipated in colis 5 and 6 is limited to the value PEC, the temperature rise should be approximatel constant for either condition of operation. The power dissipated in oeil fi should be siightly greater than P5C to allow for incomplete neutralization by colis 5 and 6 owing to individuel coi] variations. However, foi simplicity it will be considered equa] i;o P5C for the purposes of these calculations.

From Equation 7 and the weil-known laws relating to resistances The combined resistance of the windings of the relay as they appear in the circuits with both switches 8 and Il closed may be expressed as Therefore the power diSsipated in winding 5 with both switches closed may be statedas and from the design of the relay and the fact that winding 6 must neutralize win 5 PSd=PGd=%PM=%P5C (19) Substituting the values of P6 and me irom quations 16 and 17, in Equation l9, it resulte that Re=2R3 (20) Similariy, substituting the values of P502 and PZd from Euuatlons 15 and 17 in Equation 19 e result is obtained.

Wherefore, using the value of Re m Equation 20 Substltuting the values of 950 and P6d in Equa= tian 19. results that From Equations 20 and 22 the value et En as defined in Equation 14: may be obtained in terms et Ra, that is Employing this value et RP. Equatlon 24 may be restated 9R.,=2.254 2 R (Rl+2'25 (27) which may be readily solved to give Therefore all of the resistance values for the relay windings and series resistance have been stated in terms of Ra.

Returning to Equation 13 this equation may now be stated as From the foregolng it Will be apparent that a single externa1 resistance may be employed to render the power. dissipated by a relay of the type shown, independent of the number of windings enereized.

What is claimed is:

1. A relay comprising two cores, two windings on one of said cores, a single winding on the other of said cores,a pivoted armature arranged to be attracted alternatively by either core, 9. flrst circuit inciuding one of said two windings for attracting said armature to said one core, 9. second circuit including the other of said two windings and said single winding in series for attracting said armature to said other core, and a. common resistance included in both circuits, the resistance of said one winding, said single winding and said common resistance being respectively substan- R =14.8 ohms tially aine times. substantiafly two times and substantiafly one and one-hall times the resistance oi said other winding.

2. A relay comprising two cotes, two windings on one of said ocres, a single windinz on the other of said cores, a pivoted armature arranged to be attracted alternatively and oppositely in a pivotai sense by either core. 9. flrst circuit including one of said two windinn for attracting said armature to said one core. a second circuit including the other of said two windincs and said single winding in series for attracting said armature to said other core. and a common resistance included in both circuits. eflective to prevetnt overheating of said relay in either condition of attraction oi said armature. the resistances of said one winding, said single winding and said common resistance being respectivei'y snbstantiaily nine times, substantiaily two times and substantkill one and one-half times the resistance of said other winding.

3. A relay comprising two cores, two oppositely poled windings on one of said ocres, a single windin: on the other oi said cores, a pivoted armatuie arranged to be attracted a1ternatively and diapositely in a pivotal sense by either core, a flrst circuit including one 01 said two windings for energizing said one core for attracting said armaturc to said one core. 8. second circuit including the Other of said two windings and said single winding in series for substantiaily neutraiizing the energizing eflect of said one winding on said one core and for energiziug said second core for attracting said armature to said second core, and a common resistance included in both circuits, et- Iective to prevent overheating of said relay in either condition of attraction oi said armature, tire resiatances of said one winding, said single winding and said common resistance being reapectively substantiafly aine times, substantiaily two times and substantially one and one-hait times the resistance of said other winding.

4. A relay comprising two ocres, two oppositely poled windings on one of said cotes, a single winding on the other of said cores, a pivoted armature arranged to be attracted alternatively and oppositely in a pivota1sense by either core, a first circuit including one of said two windings for energizinz said one core for attracting said armature to said core, 9. second circuit incllijding the other of said two windings and said single winding in series, said other winding provided for substantiaily neutralizing the energizing eflect of said one winding on said one core and said single winding for energizing said second core for attracting said armature to said second core. and a common resistance included in both circuits, eiective to render the power dissipation by:said relay the same when said flrst circuit is ciosed alone and when both circuits are closed. the resistances of said one winding, said single winding and said common resistance being respectively substantially nine times, substantiafly two times; and substantiaily one and one-hait times the resistance ci. said other winding.

HARRY H. SCHWARIZ.

RFRENCES CITE!) The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,732,711 Boddie Oct. 22, 1929 2,297,339 Wilms et ai Sept. 29, 1942 2,303,723 Claytor Dec. 1, 1942 2,344,654 Stong Mar. 21, 1944 2,360,750 Wilms et al Oct. 17, 1944 

